1. Technical Field
The present invention relates to a liquid-ejecting head that includes a piezoelectric element, a liquid-ejecting apparatus, the piezoelectric element, and a piezoelectric material. The piezoelectric element includes a first electrode for altering the internal pressure of a pressure-generating chamber communicating with a nozzle opening, a piezoelectric layer, and a second electrode.
2. Related Art
One example of piezoelectric elements for use in liquid-ejecting heads is a piezoelectric layer between two electrodes. The piezoelectric layer is formed of a piezoelectric material having an electromechanical transfer function, such as a crystallized dielectric material. Such a piezoelectric element can be mounted on a liquid-ejecting head as an actuator in a flexural vibration mode. One representative example of liquid-ejecting heads is an ink jet print head. The ink jet print head has a diaphragm as part of a pressure-generating chamber, which communicates with a nozzle opening for discharging ink droplets. The diaphragm is deformed by a piezoelectric element to pressurize ink in the pressure-generating chamber, thereby discharging ink droplets from the nozzle opening. A piezoelectric element for use in such an ink jet print head can be produced by forming a uniform piezoelectric layer on the entire surface of a diaphragm by a film-forming technique and dividing the piezoelectric layer by lithography into pieces corresponding to each individual pressure-generating chamber.
The piezoelectric material used for such a piezoelectric element requires excellent piezoelectric characteristics (a large strain). One representative example of the piezoelectric material is lead zirconium titanate (PZT) (see JP-A-2001-223404). PZT is a ferroelectric substance. In ferroelectric substances, spontaneous polarization occurs unidirectionally, and the piezoelectric strain increases linearly with voltage applied. This facilitates the control of piezoelectric strain and the size of droplets discharged. Thus, PZT is suitable for use in actuators.
However, from the standpoint of environmental protection, there is a demand for a piezoelectric material with little or no lead. These problems are not confined to liquid-ejecting heads, including ink jet print heads, and occur in other piezoelectric elements.